1. Field of the Invention
This invention relates to electrical switches, and in particular to switches in which the actuating element is movable in response to an applied electro-magnetic signal.
2. Description of the Prior Art
Electro-magnetically operated relays are widely used in a variety of switching applications. Typically such relays are of the electro-mechanical type in which one or more contacts are actuated via a solenoid and armature arrangement. While such devices are extremely reliable, their multipart construction involves relatively high manufacturing costs and the necessary solenoid current required to operate the contacts results in a power dissipation that is both wasteful and costly. Furthermore, as it is difficult to manufacture solenoids that are both very small and efficient, a high packing density of such relays, e.g. for telecommunications switching applications, cannot be achieved. Attempts to overcome these problems have resulted in the introduction of the reed contact switch in which a pair of flexible magnetic contact blades are operated by a surrounding solenoid. However, while the reed switch goes some way to reducing size and manufacturing costs, it still suffers from the disadvantage of power dissipation.